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Disease investigators probing the mysterious neurological disorder among pork plant workers in Austin, Minn., and Indiana on Thursday said they were honing in on a specific cause.

State officials said they were broadening the investigation in Austin to thousands of former meat packers at the Quality Pork Processors plant going back a decade, to when a powerful air-compression system was installed to remove brain tissue from pig heads.

Also Thursday, the Centers for Disease Control and Prevention published the first detailed description of the disorder discovered late last year in a dozen workers at the Austin plant. They also revealed the condition’s new name – progressive inflammatory neuropathy, or PIN – and outlined how it is being investigated.

If testing proves investigators’ theory true, they will have identified a rare, new condition that could shed light on a whole family of similar disorders that are not well understood.

Officials are investigating whether pig brain tissue, liquified during removal by the air-compression system and sprayed into the air as droplets, was inhaled by workers who became sick.

This “could have far reaching applications…in terms of our understanding of the mechanism of disease,” said Ruth Lynfield, state epidemiologist, who is heading the investigation in Minnesota.

Since December, 12 meatpackers at the Quality Pork Processors (QPP) plant in Austin and two at a plant in Indiana have reported fatigue, numbness, and tingling in their arms and legs, with a wide range in severity. A few are severely disabled, while others have been treated and returned to work.

Their symptoms are like those associated with a number of diseases in which the body’s immune system attacks the nerves or the sheath that surrounds them.

All the workers were stationed near the powerful air-compression systems that blow brains out of pig heads at what is known as the head table, officials said. The process is no longer being used at either plant.

A widening probe

In Austin, the compressor system had been used since 1998. Lynfield said Thursday that investigators are now investigating any meatpackers who worked near the QPP head table since 1997. It’s an enormous task. The plant employs about 1,200 workers, many of them immigrants. Turnover is high.

“But we feel it’s important to look for prior cases,” she said.

Investigators have ruled out toxins. Viruses or bacteria are unlikely because no workers reported infectious symptoms like fever before their neurological symptoms began. That leaves the brain tissue itself.

“It makes biological sense,” said Mike Osterholm, an infectious disease expert with the University of Minnesota. In this case, he’s working as a consultant for Austin-based Hormel Foods, which doesn’t own the plant, but which uses the meat for its products. Investigators say those products are safe to eat.

An immune attack

The immune system is designed to attack entities like viruses or foreign tissue that enter the body. But for reasons that are not well understood it is not always discriminating. Sometimes it attacks the body’s own tissue, resulting in lupus, arthritis, rheumatic fever, multiple sclerosis and dozens of others auto-immune diseases.

“And pigs and humans share similarities,” said Dr. Daniel Lachance, the Mayo Clinic neurologist who first recognized the cluster of unusual cases he was seeing and who initiated the investigation.

Pigs and humans are such biologically similar mammals that researchers are trying to find ways to use pig organs to replace diseased human organs. So it’s not surprising that if the immune system creates cells to attack proteins from pig neural tissue, those immune cells might also attack human neural tissue as well, experts said. Lachance said that imaging tests show that many of the affected workers have inflammation of the nerve roots in the bottom half of their spinal cords.

“If you have a cross reaction from pig neurologic tissue and human neurologic tissue, that would make perfect sense,” Osterholm said.

Though humans have immune reactions to exposure to animal tissue – allergies, for instance – human exposure to airborne particles of pig brain tissue is a first. That makes it extremely difficult to test the exposure theory, said Lynfield.

“It has been challenging to figure out how to test that hypothesis,” she said. But now experts at the Mayo Clinic and Columbia University in New York are trying to devise ways to test pig brain tissue against the immune cells of the sick workers, she said.

It could be months before those tests are complete, she said. Meanwhile, investigators will continue to look for similar cases.

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Maybe studying this disease will lead to an understanding of how an inhaled, external element (in this case liquified pig brains) can breach the blood brain barrier and enter the CNS. I mean, isn't this not supposed to happen?

I'm hoping neurologists are following this research. It could have implications for understanding the immune process in MS.

cheerleader wrote:Maybe studying this disease will lead to an understanding of how an inhaled, external element (in this case liquified pig brains) can breach the blood brain barrier and enter the CNS. I mean, isn't this not supposed to happen?

I don't believe that the inhaled pig brains needed to cross the blood brain barrier. All that needed to happen was for the immune system to recognize the pig brain matter as foreign and then attack it. Due to a process known as molecular mimicry the immune system then recognizes a protein epitope in the worker's brain which is similar to the epitope that it attacked in the pig brain. If the proteins are similar enough, the immune system will not distinguish between the two and once it has learned to attack the pig brain it will then wreak havoc in the worker's brains.

I think there’s probably an infection involved. CIDP has many common symptoms with MS but it is much, much rarer. Basically it is where the peripheral nerves are damaged and demyelinated instead of the CNS nerves. The thing that interests me is that the acute version of CIDP is usually referred to as Guillain-Barré Syndrome…an illness which is known to frequently be preceded by viral infection.

Seeing this thread just reminds me how much I've learned about MS and the CNS in one year's time! Kind of embarrassing NHE very gently corrected me...
Still feel for these poor people, and hope they are getting treatment. That update rainer posted was sad...trying to make light of CIDP.

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